Biomass gasification in atmospheres modified by flue gas

ABSTRACT

Systems and methods are provided for generating energy from biomass. A gasifier is provided for generating syngas from the biomass. The gasifier comprises a housing for providing a first, oxygen starved environment in which the biomass is sub-stoichiometrically combusted to generate syngas—an effluent comprising gaseous combustibles. An oxidizer is connected to receive the syngas from the gasifier and configured to oxidize the syngas in a second environment distinct from the first, oxygen starved environment and to thereby generate heat energy. An oxidative agent supply mechanism introduces an oxidative agent to the first, oxygen starved environment in the gasifier housing, the oxidative agent comprising a mixture of flue gas and air.

REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/801,030 filed 8 May 2007, entitled: METHOD FOR GASIFYING SOLIDORGANIC MATERIALS AND APPARATUS THEREFOR. This application claims thebenefit under 35 USC §119(e) of the priority of U.S. provisional patentapplication No. 60/801,574 filed 18 May 2006.

TECHNICAL FIELD

This disclosure relates to the gasification of, and generating of energyfrom, solid organic materials and to the production of syngas.Particular embodiments provide methods, apparatus and systems forgasifying, and generating energy from, solid organic materials andgenerating syngas.

BACKGROUND

It has been recognized that many industrial and agricultural solidorganic by-products, such as forestry and agricultural residue, and thelike, are a potential source of chemical energy. Substantial increasesin the cost of traditional fuels, such as fuel, oil and natural gas,have provided corresponding economic incentive to try to developeffective and efficient techniques for recovering the energy in theseorganic by-products, energy that traditionally was not recovered to anysubstantial extent. Such organic materials, frequently referred to as“biomass” materials, are now successfully utilized to some extent asfuel in some large industrial systems, for example, in firing the powerboiler and the recovery boiler in a pulp or paper mill. However, thehigh capital cost that has heretofore been associated with biomassenergy recovery systems has precluded their successful use in small oreven medium-sized energy recovery systems.

Medium-sized energy recovery systems are used in community centers,schools, nursing homes, and small industrial and commercialestablishments and, to date, biomass fuels have not been satisfactorilyutilized as fuels in heating systems for such facilities. U.S. patentsdisclosing technology relating to the recovery of energy from wood chipsor similar organic materials include, for example: U.S. Pat. No.5,138,957 that issued to Morey, et al. on Aug. 18, 1992; U.S. Pat. No.4,184,436 that issued to Palm, et al. Jan. 22, 1980; U.S. Pat. No.4,312,278 that issued to Smith, et al. on Jan. 26, 1982; U.S. Pat. No.4,366,802 that issued to Goodine on Jan. 4, 1983; U.S. Pat. No.4,321,877 that issued to Schmidt, et al on Mar. 30, 1982; U.S. Pat. No.4,430,948 that issued to Schafer, et al. on Feb. 14, 1984; U.S. Pat. No.4,593,629 that issued to Pedersen, et al. on Jun. 10, 1986; U.S. Pat.No. 4,691,846 that issued to Cordell, et al. on Sep. 8, 1987; U.S. Pat.No. 4,971,599 that issued to Cordell et al. on Nov. 20, 1990, U.S. Pat.No. 6,120,567 that issued to Cordell et al. on Sep. 19, 2000 andCanadian Patent No. 2,058,103 that issued to Morey et al. on 14 Oct.1997.

However, it is not known that any of the inventions described in thesepatents have been successfully adapted to recover biomass energy on acost-effective basis in small and medium-sized energy recovery systems.

SUMMARY

Particular embodiments of the invention provide methods, apparatus andsystems for gasifying solid organic materials and generating syngaswhich may be burned to create energy. Particular embodiments providemethods and apparatus that produce high energy, low temperature, and lowparticulate-laden syngas by controlling the oxygen content in combustionair used for “starved air” combustion of biomass in a gasifier.Recirculated flue gas mixed with an amount of fresh air is utilized forproviding the oxygen content therein and for controlling the method.

Particular embodiments provide methods for gasifying biomass materials,such as forestry and agricultural residues, industrial waste materialssuch as saw mill pulp, paper products, fowl litter, such as chickenlitter and turkey litter, and hydrocarbon based plastics and the like.

Particular embodiments provide apparatus used to convert the chemicalenergy of biomass materials into thermal energy or gaseous products, andspecifically, syngas, that is also called production gas. Syngas is acompressible synthetic combustible gas containing very littleparticulate material. Thus, aspects of this invention can also be viewedas providing methods for producing syngas.

Aspects of the invention provide a method for gasifying solid organicmaterials, apparatus used in such methods, and systems incorporatingsuch methods and apparatus. One aspect of the invention provides agasifier for gasifying solid organic materials comprising in combinationa housing, wherein the housing has a lower portion and an upper portionand a cylindrical side wall supported by the lower portion and attachedto the upper portion.

In particular embodiments, the gasifier comprises a roof for thehousing, the roof being supported by and integral with the cylindricalside wall. In some embodiments, there is at least one opening throughthe roof for exiting syngas effluent and at least one opening for asensing device. In particular embodiments, the gasifier includes adevice for removing the syngas from the gasifier which is located at,and connected to, the roof opening. In some embodiments, the gasifierincludes, at the sensing device opening, one or more devices for sensingthe elevation of any mass of any solid organic material contained in thehousing. In some embodiments, the sensing device is a radar device thatis mounted over the sensing device opening and surmounts a non-metallicplate that covers the opening.

Located in the lower housing, particular embodiments of the gasifiercomprise one or more openings for supporting a device for determiningthe amount of non-combustible material (e.g. ash) remaining within thegasifier. In some embodiments, the device is located at, and connectedto, the lower portion of the housing, and within the opening fordetermining the amount of non-combustible material (e.g. ash) remainingwithin the gasifier.

In particular embodiments, the gasifier comprises one or more openingsin the cylindrical wall for supporting one or more devices for providingoxidative gas to the solid organic materials. In some embodiments, theoxidative gas comprises recirculated flue gas containing a predeterminedportion of fresh air. In some embodiments, a device for providing theoxidative gas to the solid organic materials is located in, andconnected to the oxidative gas opening.

In particular embodiments, a floor is located in the lower portion ofthe gasifier, the floor having a top surface and a bottom surface, andat least one opening therethrough to allow for the passage of solidorganic material into the interior of the gasifier. In some embodiments,the top surface of the floor comprises a retaining wall on the outsideof each of the floor openings to form a retention basin to retain thesolid organic materials in the lower portion of the gasifier to form afloorless hearth.

Particular embodiments of the gasifier include a device for moving solidorganic materials through the floor opening and into the gasifier in anupward motion and a device for providing and retaining a cone structureto the underside of the solid organic materials.

In some embodiments, the gasifier comprises a device for containing thesolid organic materials while above the retention basin and one or moreopenings in the lower portion of the gasifier to allow movement ofnon-combustibles out of the gasifier, along with a device in theretention basin for removing noncombustible materials from the gasifier.

In particular embodiments, the gasifier comprises a control and monitorfor the amount of mass of solid organic material within the gasifier anda control and monitor for the amount of non-combustibles in thegasifier.

Another aspect of the invention provides a square or rectangular “loaf”gasifier for gasifying solid organic materials. In particularembodiments, the loaf gasifier comprises a housing incorporating a lowerportion and an upper portion and four side walls supported by the lowerportion and attached to the upper portion.

The loaf gasifier has a roof supported by, and integral with, the fourside walls. In some embodiments, the loaf gasifier comprises one or moreopenings through a side wall for exiting syngas effluent and one or moreopenings through the roof for a sensing device. In some embodiments, theloaf gasifier comprises a device for removing the gaseous effluent fromthe gasifier which is located at, and connected to, the side wallopening. In particular embodiments, the loaf gasifier comprises a devicefor sensing the elevation of any mass of any solid organic materialcontained in the housing which is located at, and associated with thesensing device opening. In some embodiments, the sensing devicecomprises a radar device that is mounted over any sensing device openingand that surmounts a non-metallic plate that covers the opening.

Located in the lower housing, particular embodiments of the loafgasifier comprise one or more openings for supporting a device fordetermining the amount of non-combustible material (e.g. ash) remainingwithin the gasifier. In some embodiments, the device is located at, andconnected to, the lower portion of the housing, and within the openingfor determining the amount of non-combustible material (e.g. ash)remaining within the gasifier.

In some embodiments, the loaf gasifier comprises one or more openings inits side walls for supporting one or more devices for providingoxidative gas to the solid organic materials. In some embodiments, theoxidative gas comprises recirculated flue gas containing fresh air. Inparticular embodiments, a device for providing the oxidative gas to thesolid organic materials is located in, and connected to the oxidativegas opening.

The gasifier of particular embodiments comprises a floor located in thelower portion of the loaf gasifier, the floor having a top surface and abottom surface, and at least one opening therethrough to allow for thepassage of solid organic material into the interior of the gasifier. Insome embodiments, the top surface of the floor comprises a retainingwall on the outside of each of the floor openings to form a retentionbasin to retain the solid organic materials in the lower portion of thegasifier to form a floorless hearth.

In particular embodiments, the loaf gasifier includes a device formoving solid organic materials through the floor opening and into thegasifier and a device for providing and retaining a cone structure tothe underside of the solid organic materials.

In some embodiments, the loaf gasifier comprises a device for heatingthe solid organic materials while above the retention basin and one ormore openings in the lower portion of the gasifier to allow movement ofnon-combustibles out of the gasifier, along with a device in theretention basin for removing noncombustible materials from the gasifier.

In particular embodiments, the loaf gasifier comprises a control andmonitor for the amount of mass of solid organic material within thegasifier and a control and monitor for the amount of non-combustibles inthe gasifier.

In another embodiment, the circular gasifier described above is modifiedto alter the flow of effluent by providing a constriction in themidsection of the gasifier. This embodiment provides a gasifier forgasifying solid organic materials comprising a housing wherein thehousing has a lower portion having a top part and an upper portionhaving a bottom part. The housing has a cylindrical side wall supportedby the lower portion and attached to the upper portion. The cylindricalside wall has a constricted section where the top part of the lowerportion and the bottom part of the upper portion meet and join.

In yet another embodiment of this invention, the loaf gasifier describedabove is also modified to provide a constriction in its side walls. Thisembodiment provides a loaf gasifier for gasifying solid organicmaterials comprising a housing wherein the housing has a lower portionwith a top part and an upper portion with a bottom part. The housing hasfour side walls supported by the lower portion and attached to the upperportion. The side walls have a constricted section where the top part ofthe lower portion and the bottom part of the upper portion meet andjoin.

Another aspect of the invention provides a method for gasifying solidorganic materials to produce a gaseous effluent and a solid residue. Themethod comprises providing a supply of solid organic material andproviding a circular gasifier as set forth in this disclosure.Thereafter, the solid organic materials are introduced into the gasifierupwardly from a lower portion of the gasifier to provide a mass of solidorganic materials in the gasifier. The solid organic materials areignited and then heated in the gasifier while providing an oxidative gasto the gasifier. In particular embodiments, the oxidative gas comprisesrecirculated flue gas from a flue stack located in a system in which thegasifier is operating. In some embodiments, the oxidative gas comprisesa combination of the flue gas and a predetermined portion of fresh air.

In particular embodiments, there is provided an effluent flow path inthe gasifier for a portion of the gaseous effluent to migrate, mix, andreact through the heated solid organic materials and the syngas formedthereby is transferred outwardly from the gasifier. Non-combustiblesolids are also transferred out of the gasifier.

Another aspect of the invention provides a method for gasifying solidorganic material to produce a gaseous effluent and a solid residue. Themethod comprises providing a supply of solid organic material andproviding a loaf gasifier as set forth in this disclosure. The methodalso involves introducing the solid organic materials into the gasifierupwardly from a lower portion of the gasifier to provide a mass of solidorganic materials in the gasifier. The solid organic materials areignited and then heated in the gasifier while providing an oxidative gasto the gasifier to provide a gaseous effluent. In some embodiments, theoxidative gas comprises recirculated flue gas from a flue stack locatedin a system in which the gasifier is operating. In particularembodiments, the oxidative gas comprises a combination of the flue gasand a predetermined portion of fresh air.

In particular embodiments, there is provided an effluent flow path inthe gasifier for a portion of the gaseous effluent to migrate, mix, andreact through the heated solid organic materials and the syngas formedthereby is transferred outwardly from the gasifier. Non-combustiblesolids are also transferred out of the gasifier.

Aspects of the invention provide systems that utilize each of thevarious gasifiers disclosed.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are schematic drawings showing gasifiers, apparatus andmethods for gasification of biomass and producing syngas andcorresponding portions of systems incorporating such gasifiers accordingto an example embodiment.

FIG. 2 is a front view of a circular gasifier according to a particularexample embodiment.

FIG. 3 is a cross sectional front view of the FIG. 2 gasifier throughline A-A.

FIG. 4 is an enlarged front view of a radar sensing device.

FIG. 5 is a perspective view of a segmented, round feed cone which maybe used in gasifiers according to particular embodiments of theinvention.

FIG. 5A is a perspective view of a unitary, round feed cone feed whichmay be used in gasifiers according to particular embodiments of theinvention.

FIG. 6 is a perspective view of a segmented, square feed cone which maybe used in gasifiers according to particular embodiments of theinvention.

FIG. 6A is a perspective view of a unitary, square feed cone which maybe used in gasifiers according to particular embodiments of theinvention.

FIG. 7 is a cross sectional view of the area designated 28 of FIG. 3,showing an example of the detail of the moveable cone feed and thebottom tuyeres according to a particular embodiment.

FIG. 8 is a front view of a square or rectangular, loaf gasifier,according to a particular embodiment.

FIG. 9 is a cross sectional view of the FIG. 8 loaf gasifier throughline B-B.

FIG. 10A is a cross sectional view of an example construction of wallshaving an insulation layer which may be used with particular gasifierembodiments.

FIG. 10B is a cross sectional view of another example construction ofwalls using air as insulation which may be used with particular gasifierembodiments.

FIG. 11 is an enlarged side view of the roof the FIG. 8 loaf gasifieraccording to a particular embodiment.

FIG. 12 is a cross sectional view of the FIG. 11 roof according to aparticular embodiment.

FIG. 13 is a top view of an ash collection system suitable for use withparticular embodiments of the FIG. 8 gasifier.

FIG. 14 is an angled side view of a gasifier according to a particularembodiment, with the sides open to show its ash-removal grate system.

FIG. 15 is a side cross sectional view of the FIG. 14 grate systemthrough the line C-C.

DETAILED DESCRIPTION

FIGS. 1A and 1B (together, FIG. 1) are schematic representations ofportions of an apparatus, method and system for gasification of, andgeneration of energy from, biomass according to an example embodiment.FIG. 2 is a front view of a circular gasifier 1 suitable for use as thegasifier of FIG. 1A. FIG. 3 is a cross sectional front view of the FIG.2 gasifier through line A-A.

FIG. 1 shows a circular gasifier 1 according to a particular embodimenthaving an ash removal system 4 and a solid mass feeder 2 comprising acollection bin 5, connected by auger feed 3 to gasifier 1. In theillustrated embodiment, a portion of solid mass feeder 2 runsessentially horizontally 7 beneath gasifier 1 and then turns essentiallyninety degrees vertically 8 and thus feeds gasifier 1 from the center offloor 9 of gasifier 1 (as shown in FIGS. 2 and 3). In horizontal run 7,solid mass feeder 2 may be shrouded or may comprise an open trough. Inthe illustrated embodiment, solid mass feeder 2 is covered by a shroud 6enclosing auger feed 3 (as shown in FIG. 3).

In some embodiments, the solid mass materials are first comminuted orchopped, if it is forestry product, so that it will flow and be ignitedreadily. Generally this chopped material is best handled if the piecesare 3 inches or less in any dimension. If the solid mass material ischicken litter or turkey litter, then chopping is not required.

FIG. 2 is an enlarged front view of a circular gasifier, according to aparticular example embodiment, showing gasifier 1, auger feed 3, shroud6, horizontal run 7 and vertical run 8 of solid mass feeder 2. Gasifier1 comprises a housing 10 that has a cylindrical side wall 11 supportedby the lower portion, generally shown as 12, of housing 10. Cylindricalside wall 11 is attached to the upper portion of housing 10, indicatedgenerally as 13. Housing 10 is surmounted by a roof 14, which issupported by, and integral with, cylindrical side wall 11.

In particular embodiments, gasifier 1 is modified to alter the flow ofeffluent by providing a constriction (not shown) in the mid-section ofgasifier 1 (e.g. between the upper part of lower portion 12 and thelower part of upper portion 13). In some embodiments, the constrictionis provided in cylindrical side wall 11 and is located where the upperpart of lower portion 12 joins the lower part of upper portion 13.Constriction of the gasifier is shown in FIG. 9 with respect to the loafgasifier 60 described below.

Located in cylindrical side wall 11, particular embodiments may includeone or more openings for providing oxidative gas 121 to the solidorganic materials. In some embodiments, the oxidative gas comprisesrecirculated flue gas and fresh air. In some embodiments a device islocated in, and connected to, the oxidative gas opening for providing anoxidative gas to the solid organic materials.

In the illustrated embodiment, solid organic materials are introducedupwardly into gasifier 1 from a lower portion (e.g. lower portion 12) ofgasifier 1 to provide a mass of solid organic materials in gasifier 1.The solid organic materials are ignited and then heated in gasifier 1,while providing an oxidative gas to gasifier 1, to provide a gaseouseffluent. In particular embodiments, the oxidative gas comprisesrecirculated flue gas from a flue stack located in a system in whichgasifier 1 is operating. In particular embodiments, the oxidative gascomprises a combination of recirculated flue gas from a flue stack (e.g.117 in FIG. 1B) located in a system in which gasifier 1 is operating andfresh air.

An effluent flow path is provided within gasifier 1 for a portion of thegaseous effluent to migrate, mix, and react through the heated solidorganic materials. The syngas formed thereby is transferred outwardlyfrom gasifier 1 and any noncombustible solids are transferred out ofgasifier 1.

FIG. 3 is a cross sectional front view of gasifier 1 (shown also in FIG.2). In the illustrated embodiment, syngas exits inner chamber 62 ofgasifier 1 through exit port 15 in roof 14. Also shown in FIG. 3 is asensing device 16 that is positioned over an opening 17. Sensing device16 is a radar that is used to monitor the top of the solid mass pile 18shown in FIG. 3. For purposes of illustration, only one such device 16is shown, but more than one such device 16 may be used. Gasifiersaccording to particular embodiments use at least three such sensingdevices 16. Gasifiers according to other embodiments use at least fivesuch sensing devices 16. As described herein, sensing devices are usedto monitor the height of solid mass pile 18. It is generally desirableto maintain an appropriate height of solid mass pile 18 to producesyngas with lower amounts of particulate.

FIG. 4 is an enlarged front view of sensing device 16 shown in FIG. 3.In the illustrated embodiment of FIG. 4, sensing device 16 comprises aradar. FIG. 4 shows details of the construction of sensing device 16while FIG. 3 shows how sensing device 16 may be positioned on gasifier1.

FIG. 4 shows a radar sensing device 16 mounted on roof 14 of circulargasifier 1. Sensing device 16 is housed in an open housing 21 andsupported by adjustable fasteners 19 and has the capacity to be adjustedangularly on swivelled fasteners 20 so that sensing device 16 can sensethe contour of solid mass pile 18 in the interior of gasifier 1. In theillustrated embodiment, sensing device 16, in its housing 21, is mountedover a non-metallic plate 22. Plate 22 is generally non-metallic so thatsensing device 16 can direct a radar beam into the interior of gasifier1 and sense the top of solid mass pile 18. It should be noted that theopening 17 in gasifier 1 is only an opening in the metal cladding ofhousing 10, and not an opening through the firebrick contained in theinterior of housing 10.

Maintaining control of the height of solid mass pile 18 is desirable forcombustion control and the release of gaseous combustibles, i.e., the“product gas”. The location of feed cone(s) 25 and vertical auger(s) invertical run 8 (see FIG. 3) are designed to provide a solid mass pile 18having a generous depth, and a generally flat upper periphery. In someembodiments, this flat, mesa-like upper surface extends over 60 to 70percent of the floor area, generally filling the lower portion (e.g.lower portion 12) of gasifier 1, and sharply tapers downward adjacentside wall 11. This downward taper, referred to as the angle of repose,is dependent upon the type of fuel used. A flat fuel pile 18 may help toachieve uniform combustion without bridging. This flat configurationresults in an approximately uniform pile depth, which in turn may resultin uniform air pressure within pile 18, thus minimizing channeling ofpile 18. In addition to the flat shape of fuel pile 18, it may bedesirable to maintain a depth of pile 18. Ash may be maintained belowthe actively burning portion of pile 18 to prevent heat damage to feedcone 25 and ash removal system 4. In an example embodiment, about 6inches or more of ash is maintained below the actively burning portionof pile 18.

As the solid organic feed material in gasifier 1 moves from feed cone 25to the center and top of pile 18, it gets hotter and hotter, andvolatile components in such material and combustion products begin todissipate from the surface of pile 18, partly being assisted by thegases that are rising through such material. As the feed material inpile 18 loses more and more of the volatile and pyrolytic ingredients,it will begin to form high molecular weight carbonaceous derivatives andchar until, eventually, it is exposed to the full operating temperatureinside gasifier 1. This material moves generally horizontally outwardand then downward toward the outer wall and lower floor 9 where it isexposed to further oxidation agents via tuyere arrays 32 and 33 for amore complete reaction, at which time further organic constituents ofsuch feed material will gasify, and will pass from gasifier 1 as anincompletely oxidized gaseous effluent of combustibles (syngas). In theillustrated embodiment, the effluent is carried away from gasifier 1through an insulated exit duct. The velocity of the effluent above fuelpile 18 and through exit port 15 is kept low, reducing particulatecarryover.

In various embodiments, air-modified flue gas (oxidative gas),steam-modified ambient air or steam-modified pure oxygen is provided toburning piles 18 and 71 through the respective tuyeres fitted ongasifiers 1 and 60. Loaf gasifier 60 and pile 71 are described in moredetail below with reference to FIG. 9.

In some embodiments, the feed rate into gasifier 1 is monitored andcontrolled by monitoring and controlling the height of fuel pile 18within gasifier 1. Suitable instrumentation, not shown, is provided tocontrol the rate of the delivery of the feed material into gasifier 1 bythe feed assembly (e.g. solid mass feeder 2) as a function of theelevation of the top of the feed material in the height of pile 18. Theshape and height of feed material pile 18 may thereby be maintainedsubstantially constant.

As solid mass pile 18 burns, it creates ash, which in particularembodiments is removed from gasifier 1. Gasifier 1 of the illustratedembodiment comprises one or more trenches 24 provided in the gasifierfloor and one or more devices for removal of ash and combustion residuesand for control of the elevation of the “moving bed of ash” hearthdescribed in more detail below. In the illustrated embodiment of FIG. 3,the ash removal system 4 comprises an auger 26. FIGS. 2 and 3 show twotrench sections 24, one on either side of a centrally located feed cone25. Feed cone 25 is described in more detail below. Ash augers 26 intrench sections 24 move the ash toward points of discharge 27 suitablylocated at the ends or bottoms of trench sections 24. In the illustratedembodiment, trench sections 24 are connected to a bin or a conveyor ofsuitable design for further disposal of the ash (see ash removal system4 of FIG. 1A).

Formation of ash creates a floorless hearth 30 in gasifier 1 on whichburning solid mass pile 18 is situated. This ash build up, together withintermittent or continuous ash removal, creates a “moving bed of ash”,which provides floorless hearth 30.

In other embodiments, control of the level of the “moving bed of ash”that creates hearth 30 and removal of ash can be accomplished by aconveyor or conveyors moving across the entire floor, or sectionthereof, from side to side, or end to end of gasifier 1. In otherembodiments, a set, or sets, of dump grates can be inserted under“moving bed of ash” hearth 30 to facilitate and control removal of theash.

In some particular embodiments of the invention, for example, whenforestry products are used as the feed, ash removal system 4 comprises apeppermill grate 40 (see FIG. 7 which is a cutaway portion of FIG. 3,section 28). In the illustrated embodiment, peppermill grate 40comprises a flat metal plate 39 that is perforated with a multiplicityof holes 41 for allowing ash to fall therethrough. Over top of flatplate 39 is a moveable grate 42 that is also perforated with holes 43.Moveable grate 42 may be moved such that it covers part of holes 41 partof the time and can allow holes 43 to be aligned with holes 41, suchthat ash may fall through aligned holes 43, 41. Grate 42 may be moved ina generally oscillating motion. Ash may then fall through aligned holes41, 43 and into retention basins 29 below (see FIG. 2). Augers 26 movethe ash to discharge point(s) 27 where it is moved out of retention bins29 into a conveyor portion of ash removal system 4 (see FIG. 1A) fortransfer away from gasifier 1.

FIG. 7 further shows a portion of a segment of feed cone 25 surmountinggrate 42. Grate 42 is surmounting flat plate 39. At one edge 44 of grate42 of the illustrated embodiment, there is a pin 45 that attaches grate42 to flat plate 39. Grate 42 may partially swing around pin 45 suchthat grate 42 moves in an oscillating motion. The swinging motion ofgrate 42 moves the ash that piles on grate 42 and flat table 39 and theash falls through holes 41 and 43 into basin 29 below. Also shown inFIG. 7 are bottom tuyeres 34, which are described in more detail below.

FIG. 14 is an angled side view of a gasifier 1 according to anotherembodiment with its sides open to show another type of grate system 84,which is similar to peppermill grate 40 of FIG. 7. FIG. 15 is a sidecross sectional view of grate system 84 through the line C-C. Gratesystem 84 comprises two grates 85 and 86 (see FIG. 15) at the bottom ofgasifier 1. In the illustrated embodiment, bottom grate 85 is stationaryand has openings 87. In particular embodiments, openings 87 areapproximately 8 inches wide by 20 inches long. Top grate 86, which alsohas openings 88, is moveable relative to bottom grate 85. In theillustrated embodiment, top grate 86 is moved by two hydraulic cylinders(not shown). In particular embodiments, the hydraulic cylinders have astroke maximum of about 8 inches. Because grate ring 86 is round, thisstroke rotates grate ring 86. The hydraulic cylinders stroke top grate86 such that it aligns openings 87, 88 and, on the back stroke,misaligns openings 87, 88.

In the illustrated embodiment of FIG. 15, top grate 86 has wedge plates89 mounted on top of it. These plates 89 are installed in such a waythat when the top grate 86 is rotating, wedge plates 89 push the ash infront of them towards the openings 87 in the bottom grate 85. Themovement and height of wedge plates 89 ensure measurable ash removalfrom the bottom of pile 18, and can prevent the ash bridging above theash grate openings.

As the bottom layer of ash is discharged, the mixture of ash andunburned carbon from above drops down lower. As the carbon burns, theprocess temperature in the vicinity of the ash discharge thermocouples(for example, temperature probes 53 described below) becomes higherindicating that the system has to wait for the next ash dump. As thecarbon is more and more combusted and disintegrates, the bottom ofgasifier 1 becomes colder and colder indicating that only ash is left atthe bottom of gasifier 1 and it is time for a new ash dump.

Where the feed material into gasifier 1 is soft, easily combustiblematerial, such as chicken litter, turkey litter, or plastics, and thelike, a peppermill grate system (e.g. peppermill grate system 40 of FIG.7 or grate system 84 of FIG. 14) may not be used.

For circular gasifier 1 of FIGS. 2 and 3, feed cone 25 is alsocircular—see FIGS. 5 and 5A. As shown in FIG. 3, feed cone 25 iscentrally located and arranged along the centerline of the chamber ofgasifier 1 and protrudes above the general elevation of the “moving bedof ash” hearth 30. In the illustrated embodiment, feed cone 25 isserviced by a single, or twin set, of vertical fuel feed augers 31 tomove feed material through vertical run 8. For the loaf type gasifier 60of FIGS. 8-9 (described below), which has a rectangular profile, feedcone 25 is also square or rectangular—see FIGS. 6 and 6A. Feed cones 25may move solid organic material upwardly into gasifier 1 and may providea cone-like structure to the underside of solid organic material pile 18or 71.

In particular embodiments, feed cones 25 comprise a single piece, thatis a unitary article, for example as shown in FIGS. 5A and 6A,respectively. In other embodiments, feed cones 25 are segmented as shownin FIGS. 5 and 6 so that they can more easily be moved into and out ofgasifier 1 or 60 respectively, for servicing, maintenance and repair.The individual segments of segmented feed cones 25 can be simply set inplace adjacent each other, or they can be mortared together, or gluedtogether to hold them in place. The segmented feed cones 25 shown inFIGS. 5 and 6 may be used to implement the moveable feed cones 25described below.

Feed cones 25 may be moveable or non-moveable. In particularembodiments, feed cones 25 may be moved such that they oscillate in apartial circular motion within gasifier 1. A moveable feed cone 25provides relatively even introduction of oxidative gases through burningsolid mass pile 18, which may in turn minimize creation of gas channels.Periodic movement of feed cone 25 also prevents oxidative gas fromburning holes between the gas sources and the surface of pile 18.

Within gasifier 1, combustion is carried out sub-stoichiometrically withthe application of an oxidizing agent. In particular embodiments, theoxidizing agent comprises flue gas mixed with fresh air. Solid organicmaterials are transferred continuously or intermittently to gasifier 1at a rate to maintain a mass of solid organic materials in gasifier 1.The oxidizing agent is continuously added to gasifier 1 to continuouslygasify the solid organic materials in solid mass pile 18, and the solidresidue (non-combustibles) are transferred out of gasifier 1, forexample, as described above. In particular embodiments, the oxidizingagent is administered through a set or sets of suitable ducts connectedto nozzles, for example, tuyeres and injection points located within,around and between feed cones 25, and to a row, or line of nozzlesand/or tuyeres in the surrounding walls of gasifier 1.

FIG. 3 shows upper tuyeres 32 and lower tuyeres 33 in side walls 11 ofgasifier 1 and bottom tuyeres 34 in feed cone 25. Tuyeres 32, 33, 34 areused to facilitate the movement of the oxidizing agent (e.g.air-modified flue gas) to gasifier 1 and into burning solid mass 18. Inthe illustrated embodiment, upper tuyeres 32 are fed through a commonmanifold 35 and lower tuyeres 33 are also be fed through a commonmanifold 36. Tuyeres 32 are linked to manifold 35 by feed tubes 37 andtuyeres 33 are linked to the manifold 36 by feed tubes 38 (see FIG. 2).

In the embodiment shown in FIGS. 2 and 3, manifolds 35 and 36 are fedfrom a flue gas return system 48 that includes a duct 49 and an airmotor 50. Inlet 51 of air motor 50 is attached to system 200 (FIG. 1B)for supplying air-modified flue gas to flue gas return system 48.

Gasifier 1 is equipped with an exit port 15 for the movement of syngasproduced therein. In the illustrated embodiment, a fixture 52 issurmounted on exit port 15 for allowing the attachment of components(described below) which may be used to handle the syngas.

In the illustrated embodiment, the lower portion (e.g. lower portion 12)of housing 10 of gasifier 1 includes one or more devices (e.g. probes53) for determining the amount of non-combustibles (e.g. ash) withingasifier 1. Probes 53 can be used to monitor the level of a moving ashbed defined by the upper elevation of the accumulated ash. As anexample, probes 53 may comprise a pair or pairs of thermo elementslocated one above the other, distanced such that the level of the movingash bed is in between them, and capable of characterizing thetemperature of, and the difference in temperatures between, the materialabove and below the moving ash bed in operation. This temperaturedifference can then be used to dictate the degree of movement of ashremoval auger(s) 26 and to thereby control the level of the moving ashbed. In particular embodiments, gasifier 1 is equipped with several setsof probes 53, inserted through openings 55, around the perimeter of thegasifier chamber. In such embodiments, an average of probe 53 input datais used determine the desired movement of ash removal auger(s) 26.

Lower portion 12 of gasifier 1 includes a floor having a top surface anda bottom surface. The gasifier floor may have one or more openingsthrough it to allow for the passage of the solid organic material intothe interior of gasifier 1. In the illustrated embodiment, the topsurface of the floor is provided with a retaining wall on the outside ofthe floor openings to form a retention basin to retain the solid organicmaterials in lower portion 12 and to thereby form floorless hearth 30.

To bring gasifier 1 to an operational condition on start up, solid massfeeder 3 is activated to form pile 18 of feed material in gasifier 1 inpreparation of development of a “moving ash bed” above gasifier floor 9.Pile 18 of feed material is ignited. To bring pile 18 of feed materialup to its normal operating temperature, fuel oil or other readilycombustible supplemental fuel may be added to it. As an example, thismay be done manually through an opening 54 provided in the wall ofgasifier 1.

As the oxidation proceeds and the temperatures elevate, the solid massin pile 18 pyrolyzes and gasifies. Combustion of the solid mass may takeplace below the top of pile 18. Gas produced in the starved combustionsifts through burning pile 18 and into the upper portion of burning pile18, pile 18 acting as a filter for particulate material. The products ofcombustion rise through pile 18 and cool because the latent heat ofwater absorbs the energy. As fuel is delivered, it gets pyrolyzed andthe fuel moisture and volatile hydrocarbons are separated from thenon-volatile components. These processes are driven by the hot gasesthat result from the combustion of the fixed carbon, which takes placebelow the top of pile 18.

The moderately slow burning lower portion of pile 18 serves to establisha quiet oxidation zone whereby entrainment of particulate matter and flyash is minimized or reduced. In particular embodiments, gasifier 1produces syngas with a maximum of combustible gaseous components and aminimum of particulate matter.

FIG. 8 is a front view of a loaf type gasifier 60, according to anotherembodiment. FIG. 9 is a cross sectional view of the FIG. 8 gasifier 60,through line B-B. Gasifier 60 is defined by four vertical side walls 61,giving the chamber of gasifier 60 a square or rectangular cross sectionand forming an enclosure 62 (FIG. 9) which has an irregularly shapedbottom 63. Gasifier 60 includes a roof 64, which in cross section may bevaulted, tapered or flat or any combination thereof.

In particular embodiments, walls 61 are made up of a multiplicity oflayers. FIGS. 10A and 10B show cross-sections of walls 61 according toparticular embodiments. In the embodiment of FIG. 10A, the innermostlayer 65 is an insulating layer of a high-temperature resistant typerefractory that is capable of withstanding the elevated temperaturesthat develop within gasifier 60, for example, temperatures in the rangeof approximately 2300° F. to approximately 2500° F. Suchhigh-temperature resistant type refractory is capable of withstandingoperational temperature variations as well as the corrosive, erosiveeffects of the gaseous materials produced by the oxidation of biomassfeed material that is delivered into gasifier 60. Walls 61 may alsoinclude an insulating layer 66 on the outside of wall layer 65 tofurther prevent loss of heat through walls 61 of gasifier 60. As anexample, insulating layer 66 may comprise a single layer of insulatingfirebrick, block insulation, or blanket insulation. In the illustratedembodiment, the outer casing of the wall 61 is a structural layer orshell 67 comprising sheet metal, for example, plate steel, which isairtight and provides the necessary strength and rigidity for walls 61.

FIG. 10B shows second embodiment of wall 61, wherein insulating layer 66is not used, and a vacant layer or space 68 is provided betweenrefractory innermost layer 65 and shell 67. The air which fills vacantlayer 68 acts as an insulator between refractory layer 65 and shell 67.This warmed air in vacant layer 68 can also be used as a source ofpreheated air for injection into gasifier 60 and recovery andregeneration equipment 96 and 98 (see FIG. 1) which are described inmore detail below.

Referring to FIGS. 8 and 9, the biomass feed material from the storagehopper assembly (not shown) is introduced into gasifier 60 from belowgasifier 60 through at least one feed cone 59. In the illustratedembodiment, feed cone 59 is located along the centerline of bottom 63 ofgasifier 60. During normal operating conditions, the feed material risesover the top of feed cone(s) 59 and rests on hearth 70 until it forms apile 71 of such material, which is the normal or equilibrium conditionof gasifier 60. Hearth 70 is made up of ash and other solid combustionresidues. This self-generated hearth 70 is similar to the “moving ashbed” configuration that was described above in connection with gasifier1. As primary oxidation progresses, this bed continues to elevate andthe ash is removed at essentially the same rate it is formed to maintainthe appropriate height of fuel pile 71.

As described above for gasifier 1, the height of pile 71 may becontrolled to control combustion and the release of gaseouscombustibles. The principles discussed above for the control of pileheight in gasifier 1 apply for gasifier 60 and will not be repeatedherein.

In the illustrated embodiment (see FIGS. 9, 11 and 12), exit ports 69are positioned so as to vent gasifier 60 through roof 64. It should benoted that prior art loaf gasifiers required that the exit for the gasesproduced therein must be through the side wall to minimize the flow ofparticulate materials along with the gas. In particular embodiments,side walls 61 are provided in a height which allows any air-borneparticulate to fall back to pile 71 rather that exit via ports 69. Thepositioning of exit ports 69 within gasifier 60 can be as shown in FIGS.9, 11 and 12, may be sloped or vertical, and is selected to be practicaland suitable for the specific application.

As in gasifier 1 described above, an oxidizing agent is administeredthrough a set or sets of suitable ducts connected to nozzles, forexample tuyeres, and injection points located within, around and betweenfeed cones 59, and to a row, or line of nozzles and/or tuyeres in thesurrounding walls 61 of gasifier 60.

FIG. 9 shows upper tuyeres 73 and lower tuyeres 74 in side walls 61 andbottom tuyeres 75 in feed cone 59; all of which, in particularembodiments, are used to facilitate the movement of the oxidizing agent(e.g. air-modified flue gas) to gasifier 60 and into burning solid masspile 71. In the illustrated embodiment, upper tuyeres 73 are fed througha common manifold 76 and lower tuyeres 74 are also fed through a commonmanifold 77. In the illustrated embodiment, tuyeres 73 are linked tomanifold 76 by feed tubes 78 and tuyeres 74 are linked to manifold 77 byfeed tubes 79.

System 200 (FIG. 1) for supplying fresh air-modified flue gas may alsobe used in conjunction with gasifier 60. Manifolds 76 and 77 of gasifier60 are fed from a flue gas return system, generally 48 (see FIG. 8),which comprises a duct 49 and an air motor 50. In the illustratedembodiment, the inlet 51 of air motor 50 is attached to system 200(FIG. 1) for supplying fresh air-modified flue gas to flue gas returnsystem 48. The details of the movement of the fresh air-modified fluegas from flue stack back to gasifier 60 are set forth in detail below.

In the illustrated embodiment of gasifier 60, the upper part of lowerportion 12 and the lower part of upper portion 13 (see FIG. 3 forreference to lower portion 12 and upper portion 13) provide aconstriction 80 in the interior chamber 62 of gasifier 60. In theillustrated embodiment, constriction 80 is built into layer 65, or itcan be formed from a plate that is set at an angle into layer 65.Constriction 80 slows down the upward flow of product gas and therebyassists in reducing the amount of particulate material that tends toreach exit ports 69.

In the illustrated embodiment, feed rate into gasifier 60 is monitoredand controlled by monitoring and controlling the height of fuel pile 71within gasifier 60 using the same sensing devices 16 (e.g. radar sensingdevices 16) as described above. Suitable instrumentation, not shown, isprovided to control the rate of the delivery of the feed material intogasifier 60 by the feed assembly as a function of the elevation of thetop of the feed material in the height of pile 71, in some embodimentsto maintain such elevation at a substantially constant value, andthereby to contain the pile 71 of feed material at a substantiallyconstant size.

FIG. 11 is an enlarged front view of roof 64 of loaf gasifier 60. FIG.12 is a cross sectional view of roof 64, showing the construction of thewalls of roof 64. In the illustrated embodiment, roof 64 comprises twoexit ports 69 for syngas. Also shown in FIG. 11 is a placement of radarsensing device 16 on roof 64, between exit ports 69. Dotted lines 184(shown in FIG. 9) illustrate the beam of radar sensing device 16penetrating into the interior 62 of gasifier 60. In the illustratedembodiment, roof 64 comprises an outer steel wall 67, insulating layer66 and interior refractory layer 65. In the illustrated embodiment,component 82 is a flange useful for fitting the roof 64 to the sidewalls 61 of gasifier 60.

FIG. 13 is a cross sectional view showing a number of components of theash handling system 81 of loaf gasifier 60. Ash handling system 81 ofthe illustrated embodiment comprises removable grates 42, increasingflight ash removal augers 26 in collection bin and retention bin 29, andcastable tuyere panels 83. FIG. 13 also shows the exit of centered feedcone 59.

FIGS. 1A and 1B schematically depict gasifier 1 in use with a system 200for generating energy from biomass materials. System 200 incorporatesone or more methods according to a particular embodiment of theinvention.

As discussed above, gasifier 1 is fed a solid mass material using solidmass feeder 2 comprising auger feed 3, and ash is removed from gasifier1 by ash removal system 4. Syngas 90 that is produced by the pyrolysisand gasification of the solid mass material exits gasifier 1 throughexit port 15 into syngas burner 91. Syngas 90 is controlled by draftcontrols 93. In the illustrated embodiment, syngas burner 91 is aided incombustion using a combustion air blower 94 that provides air 95 tosyngas burner 91.

In particular embodiments, syngas 90 is provided to syngas burner 91 ata temperature of about 500° F. to about 600° F. and is in a starved aircondition. This contrasts with prior art systems in that the normaltemperature of the syngas from prior art devices is in the range of1200° F. to 1400° F., and in prior art systems, this syngas is not“starved air” and before the prior art syngas can be used, it has to becooled and compressed, requiring additional and expensive equipment.Syngas burner 91 heats and combusts syngas 90, for example, up to atemperature in the range of 1200° F. to 1400° F. before the syngas isprovided to a low NO_(x) oxidizer 96.

Syngas 90 may be provided to a kiln 98 using syngas blower 99 that movessyngas 90 to a nozzle mix syngas burner 100. Thereafter, syngas 90 ismoved through nozzle mix syngas burner 100 into kiln 98. Hot gas stream107 (about 2200° F.) output from kiln 98 is moved to low NO oxidizer 96and combined with the oxidation product 97 coming from syngas burner 91.

In the illustrated embodiment, the heating and movement of the gases inkiln 98 is aided by mixing heated air 101 from a heat exchanger 102 (seeFIG. 1B) with heated ambient air 105 to form heated air stream 103 whichis bled into nozzle mix syngas burner 100 using a preheated combustionair blower 104. A portion 106 of heated air 101 from heat exchanger 102(FIG. 1B) is also bled directly into kiln 98.

Hot gas stream 107 output from kiln 98 is fed into low NO_(x) oxidizer96 and mixed therein with the oxidation product 97 from syngas burner 91being fed into the top portion of the low NO_(x) oxidizer 96. Low NO_(x)oxidizer 96 is fed ambient air 108 using a combustion/tempering air fan109, through manifolds 110 and tuyeres (not shown) and the flue gas 111that exits low NO_(x) oxidizer 96 does so at about 2000° F. and passesto heat exchanger 102 shown in FIG. 1B.

FIG. 1B shows heat exchanger 102 into which flue gas 111 from low NOoxidizer 96 has been passed. Exchanged (cooled) flue gas 112 is thenpassed to a metal heat exchanger 113, for example, at about 1400° F.Metal heat exchanger 113 is useable because of the relatively lowertemperature of cooled flue gas 112 as compared to flue gas 111 inputinto heat exchanger 102 which is at about 2000° F. Air 114 output frommetal heat exchanger 113 becomes the input air to heat exchanger 102. Inthe illustrated embodiment, the movement of air 114 is aided by theintroduction of fresh air 124 using an air blower 125.

Air 101 is the exchanged air output from heat exchanger 102 and has atemperature, for example, in the range of about 400° F. to 1200° F. Air101 is passed back to kiln 98 (FIG. 1A). In the illustrated embodiment,air 101 is occasionally vented (as shown at 116) to control thetemperature and pressure thereof.

Heat-exchanged flue gas 127 from metal heat exchanger 113 (FIG. 1B) ismoved to an induction draft fan 115 before it enters stack 117. Prior toexhaust flue gas 122 exiting flue stack 117, a portion of flue gas 120is withdrawn from stack 117 and moved to a flue gas eductor 118, whichis aided by an induced draft fan 119. At this point, fresh air 128 isinducted and mixed with flue gas 120 and it is this flue gas modifiedwith fresh air 121 that is moved back to gasifier 1 as the oxidative gasfor use in gasifier 1. Also shown in FIG. 1B is sampling port 129.

1. A system for generating energy from biomass, the system comprising: agasifier comprising a housing for providing a first, oxygen starved,environment in which the biomass is sub-stoichiometrically combusted togenerate syngas; an oxidizer connected to receive syngas from thegasifier and configured to oxidize the syngas in a second environmentdistinct from the first, oxygen starved environment and to therebygenerate heat energy; an oxidative agent supply mechanism forintroducing an oxidative agent to the first, oxygen starved, environmentin the gasifier housing, the oxidative agent comprising flue gas.
 2. Asystem according to claim 1 wherein the oxidative agent comprises amixture of flue gas and air.
 3. A system according to claim 2 whereinthe flue gas comprises recirculated flue gas generated by the oxidationof syngas in the oxidizer.
 4. A system according to claim 3 wherein theoxidative agent consists essentially of a mixture of flue gas and air.5. A system according to claim 3 wherein the oxidative agent supplymechanism comprises an eductor connected to educe the flue gas from aconduit at a location downstream from the oxidizer and connected to asource of air, the eductor operative to mix the flue gas and the air toprovide the oxidative agent.
 6. A system according to claim 3 comprisingan air supply mechanism connected to introduce air to the secondenvironment of the oxidizer, the introduced air making the secondenvironment an air-enriched environment.
 7. A system according to claim3 further comprising at least one heat exchanger located downstream ofthe oxidizer, through which the recirculated flue gas is directed priorto being introduced to the first, oxygen starved environment in thegasifier housing.
 8. A system according to claim 3 further comprising atleast one NO_(x) oxidizer located downstream of the oxidizer, andthrough which the recirculated flue gas is directed prior to beingintroduced to the first, oxygen starved environment in the gasifierhousing.
 9. A system according to claim 3 wherein the oxidative agentsupply mechanism comprises a plurality of conduits arranged to deliverthe oxidative agent into the biomass within the gasifier.
 10. A systemaccording to claim 9 wherein the housing of the gasifier comprises aside wall and the oxidative agent supply mechanism comprises a pluralityof conduits for delivering the oxidative agent through the side walls ofthe gasifier.
 11. A system according to claim 9 wherein the gasifiercomprises a feed cone, the feed cone penetrated by a generallyvertically oriented feed bore through which biomass may be introduced tothe housing of the gasifier and wherein the oxidative agent supplymechanism comprises a plurality of conduits for delivering the oxidativeagent through the feed cone and into the biomass within the housing ofthe gasifier.
 12. A system according to claim 11 wherein the feed conecomprises an upwardly facing concave surface surrounding the feed boreand a frustro-conical exterior surface surrounding the upwardly facingconcave surface and wherein the plurality of conduits for delivering theoxidative agent through the feed cone comprises a first plurality ofconduits located to introduce oxidative agent through the upwardlyfacing concave surface and a second plurality of conduits located tointroduce-oxidative agent through the frustro-conical exterior surface.13. A system according to claim 12 wherein an interior of the housing ofthe gasifier is generally rectangularly shaped and the frustro-conicalexterior surface comprises a rectangular frustro-conical surface.
 14. Asystem according to claim 12 wherein an interior of the housing of thegasifier is generally circularly shaped and the frustro-conical exteriorsurface comprises a circular frustro-conical surface.
 15. A method forgenerating energy from biomass, the method comprising: providing afirst, oxygen starved environment; sub-stoichiometrically combusting thebiomass in the first, oxygen starved environment to generate syngas;oxidizing the syngas in a second environment distinct from the firstenvironment to thereby generate heat energy; whereinsub-stoichiometrically combusting the biomass in the first, oxygenstarved environment comprises introducing an oxidative agent to thefirst, oxygen starved environment, the oxidative agent comprising fluegas.
 16. A method according to claim 14 wherein the oxidative agentcomprises a mixture of flue gas and air.
 17. A method according to claim15 wherein the oxidative agent consists essentially of a mixture of fluegas and air.
 18. A method according to claim 15 wherein introducing theoxidative agent to the first, oxygen starved environment comprisesrecirculating flue gas generated by the oxidation of the syngas in thesecond environment and mixing the recirculated flue gas with air toprovide the oxidative agent.
 19. A method according to claim 17comprising recovering heat from the recirculated flue gas prior tointroducing the recirculated flue gas into the first, oxygen starvedenvironment.
 20. A method according to claim 18 comprising introducingair into the second environment to make the second environment an airenriched environment.
 21. A method according to claim 15 whereinintroducing the oxidative agent to the first, oxygen starved environmentcomprises introducing the oxidative agent to the first environment fromlocations beneath the biomass and from locations beside the biomass. 22.A method according to claim 18 wherein a temperature of the syngasgenerated by sub-stoichiometrically combusting the biomass in the first,oxygen starved environment is less than about 600° F. and a temperatureof an oxidation product resulting from oxidizing the syngas in thesecond environment is greater than about 1200° F.
 23. A method accordingto claim 18 wherein the temperature of the oxidation product resultingfrom oxidizing the syngas in the second environment is about 2000° F.24. A method according to claim 15 wherein a temperature of the syngasgenerated by sub-stoichiometrically combusting the biomass in the first,oxygen starved environment is less than about 600° F. and a temperatureof an oxidation product resulting from oxidizing the syngas in thesecond environment is greater than about 1200° F.